Smartcard and method for production of a smartcard

ABSTRACT

The invention relates to a smart card and also to a method of producing such a smart card having a card body ( 11 ), at least one recess ( 12   a,    12   b ) arranged therein for receiving at least one chip module ( 16 ) having module connections ( 17 ) in the edge region ( 16   a ) of the chip module ( 16 ) and a conductive structure body embedded in the card body ( 11 ) and having body contact connections ( 13 ), in particular an antenna having antenna connections which are arranged below the edge region ( 16   a ) of the chip module ( 16 ), where, with the chip module ( 16 ) installed between the module connections ( 17 ) on the one hand and the body contact connections ( 13 ) on the other hand, adhesive parts ( 14 ) preferably applied at points and made of elastic, conductive material are arranged between the connections ( 13, 17 ) with pressure being applied to produce a contact.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Application No. 102 54111.2, filed Dec. 5, 2002, which application is incorporated hereinfully by this reference.

BACKGROUND OF THE INVENTION

The invention relates to a smart card and also to a method of producingsuch a smart card having a card body and at least one recess arrangedtherein for receiving at least one chip module having module connectionsin the edge region of the chip module and a conductive structure bodyembedded in the card body and having body contact connections, inparticular an antenna having antenna connections which are arrangedbelow the edge region of the chip module, according to the preambles ofpatent Claims 1 and 7.

Such smart cards are generally designed as credit cards, bank cards,electronic wallets, etc. and are used to make transactions without usingcash, such as for example to pay transport costs on public transport orto pay a purchase price for goods or services. Furthermore, such a smartcard can also be used as an ID card for a contactless access controlsystem.

Smart cards usually have a recess for receiving a chip module whichcomprises an integrated circuit for storing, processing and/orrecognizing information that is exchanged with a device, with the smartcard either being inserted into the device or brought into the vicinitythereof.

In addition, contactless smart cards for power and data transmission atrelatively low frequencies comprise antennas which are generallylaminated into the card body and the antenna connections of which mustbe electrically connected to module connections of the chip module thatis inserted.

Conventionally, there are two methods that are frequently used toproduce conductive contacts between module connections and antennaconnections lying therebelow in the case of methods for producing dualinterface cards. In the so-called ACF method, a hot-melt orthermoplastic adhesive with conductive particles arranged therein isarranged so as to produce an electrical connection between contactconnections arranged on the underside of the module and laterallyprotruding antenna connections arranged therebelow, in which theadhesive is applied to a surface of the card body in the region of therecess into which the chip module is inserted. Following installation ofthe chip module, the conductive particles produce an electrical contactbetween the module connections and the antenna connections lyingtherebelow. For this, the hot-melt or thermoplastic adhesive is heatedand cured after it has been applied and following installation of thechip module, taking account of specific values for the parameters oftemperature, pressure and duration. Such a method is illustrated forexample in DE 197 09 985 A1.

In the event of frequent bending stresses, such cured hot-melt andthermoplastic adhesives, which at the same time produce a mechanicalconnection between chip module and card body, result in a loosening ofthe electrical connections on account of the plastic and elasticdeformability properties of the hot-melt and thermoplastic adhesives.The result is an electronically unreliable connection in the smart card,which for example is of the dual interface type.

DE 197 47 388 C1 discloses another method for the electrical connectionof antenna connections and chip module connections using a conductiveliquid adhesive. In a recess (cavity) within the card body that isprovided for receiving the chip module, at least one bore is made froman edge adhesive region, provided for the adhesion of the chip module,to the antenna connections lying therebelow, in order to introduce intosaid bore, in a metered manner, a conductive liquid adhesive. Followingsuch a metering, the chip module is placed directly thereon using anadhesive applied to the adhesive region. The adhesive is cured at apredetermined temperature by the action of heat or, if two-componentadhesives are used, by exothermic reactions. On account of its stiff andhard properties and also different adhesion properties with respect tothe parts that are to be connected, such adhesives frequently exhibit,in the event of frequently occurring dynamic loads as may arise as aresult of the smart card being wrongly pushed into a cash machine or asa result of the smart cards being kept in a wallet that is designed tobe flexible per se, breaks in the cohesion and/or adhesion in theadhesive on account of overstretching and fatigue phenomena.

Accordingly, it is an object of the present invention to provide a smartcard having an inserted chip module and a conductive structure body,such as an antenna, integrated in the smart card, which ensures apermanent electrical connection between chip module connections and bodycontact connections even in the event of high and frequent bendingstress, and also to provide a method of producing such a smart card.

This object is achieved by a smart card having the features of patentClaim 1 and by a production method having the features of patent Claim7.

An essential point of the invention is that, in a smart card having acard body, at least one recess arranged therein for receiving at leastone chip module having module connections in the edge region of the chipmodule and a conductive structure body embedded in the card body, suchas an antenna having antenna connections which are arranged below theedge region of the chip module, with the chip module installed betweenthe module connections on the one hand and the body contact connectionson the other hand, adhesive parts made of elastic, conductive materialare arranged between the connections with pressure being applied toproduce a contact. Such adhesive parts are preferably applied at pointsto the body contact connections or the module connections and curedprior to installation of the chip module. The chip module is theninstalled in the card body, as a result of which the adhesive parts arepressed together as a resilient buffer between the connections andproduce a permanent, flexible, electrical contact between the moduleconnections and the body contact connections on account of their elasticproperties.

BRIEF SUMMARY OF THE INVENTION

By using a highly filled silicone-based adhesive that is preferablyliquid at the start and is subsequently solidified prior to installationof the chip module, an electrically conductive bump is obtainedfollowing installation of the chip module, which bump, even in the eventof high and frequent bending stress of the smart card, neither exhibitstears nor allows an interspace to develop between the adhesive parts andthe module connections or body contact connections.

Preferably, the adhesive parts are arranged within cutouts which arearranged in the card body below the edge region of the chip module andat the bottom terminate with the body contact connections. Such cutoutshave a volume size that is sufficient to completely receive the adhesiveparts under the application of pressure.

In the direction of the card body thickness, the height dimensions ofthe cutouts are smaller than the height of the applied adhesive parts,without the application of pressure, that is to say prior toinstallation of the chip module. The applied adhesive parts arepreferably 0.05-0.15 mm higher than upper edge regions of the cutouts inwhich the adhesive parts are arranged.

According to the method of producing smart cards, the adhesive ispreferably first inserted into the cutouts in drop form and then onewaits for it to solidify. This is effected by means of a special machinedeveloped for this purpose, which first dispenses the drop of adhesivein the μl order of magnitude and then removes itself from the drop via arapid pull-off movement in order to avoid so-called drop noses. In thisway, hemispherical surfaces of the drop. of adhesive are advantageouslyobtained, and these are critical for the elastic action of such a bump.

In order to obtain information about the quality of the shape of thehemispherical surface, a measurement of the surface structure is thencarried out using a laser beam device which takes reflectionmeasurements at the hemispherical surface and the surface structuresurrounding the latter.

Following the application of such a drop-shaped adhesive part, stackingof the individual smart cards takes place for about 2-3 hours in orderfor the adhesive parts to cure. The chip modules are then implanted intothe smart cards which are taken individually from the stack. The curedadhesive parts act as flexible bumps which ensure contact between theconnections even in the event of bending of the smart card.

Following installation of the chip module, the adhesive parts arepressed downwards by the module connections of the chip module andthereby undergo expansion in the longitudinal and width directions ofthe smart card. As soon as the module connections have been placed onthe upper edge region of the cutouts, virtually the entire volume sizeof the cutouts is filled with the pressed-together adhesive parts. Inthis way, further expansion of the adhesive parts is avoided even in theevent of many years' use of the smart card, as a result of which theformation of interspaces between the module connections or body contactconnections and the adhesive parts made of elastic material can beavoided.

Further advantageous embodiments emerge from the subclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Advantages and expediencies can be gathered from the followingdescription in conjunction with the drawing, in which:

FIG. 1 shows a cross-sectional view of a detail of a smart cardaccording to the prior art;

FIG. 2 shows a plan view of a recess for receiving a chip module of asmart card according to the prior art;

FIG. 3 shows a cross-sectional view of a detail of a smart cardaccording to one embodiment of the invention prior to installation ofthe chip module, and

FIG. 4 shows a cross-sectional view of the detail of the smart cardaccording to the embodiment of the invention shown in FIG. 3 followinginstallation of the chip module.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a cross-sectional view of a detail of a smart cardaccording to the prior art, in which according to the abovementioned ACFmethod a card body 1, in which there is arranged a conductive structurebody, such as an antenna having antenna connections 2, is connected to achip module 3 by means of a hot-melt adhesive. The chip module 3 on itsunderside has module connections 3 a which must be electricallyconnected to the antenna connections 2 following installation of thechip module.

In order to electrically connect the connections 2 and 3 a, conductiveparticles in the form of silvered glass beads 5 having a diameter ofabout 50 μm are arranged in the hot-melt adhesive 4, which conductiveparticles bring about contacting of the connections in the intermediateregion between the connections 2 and 3 a, as is shown by reference 5 a.

After bending and torsion tests have been carried out, such smart cardsproduced according to the ACF method exhibit a considerable loss ofquality in respect of the electrical connection between the connections2 and 3 a, even at a bending stress of 750 to 1000 bends.

FIG. 2 shows a plan view of a recess (cavity) that is arranged within acard body (not shown here) and is designed to receive a chip module, asis known from the prior art. The recess consists of an adhesive area 6for adhesively bonding the chip module to the card body and of an area 7that lies somewhat deeper and provides enough free space for theunderside of a chip module. In this way, the chip module is mounted in a“floating” manner, so to speak, in the card body, to which it is fixedlyconnected only in its edge region.

Additional bores 8 are arranged in a downwardly running manner from theadhesive area 6 towards the antenna connections lying therebelow, inorder to arrange conductive liquid adhesive therein. Following themetering of the adhesive into the bores 8, the chip module isimmediately placed on the adhesive area 6 and curing of the adhesiveused is brought about by the action of heat.

By virtue of the conductive adhesive in the bores 8, there is anelectrical connection between the antenna connections (not shown here)and the module connections of the inserted chip module that liethereabove (not shown here).

As a result of overstretching and fatigue phenomena caused by dynamicloads acting on the smart card from outside, such an adhesive connectionexhibits the formation of tears.

FIG. 3 shows a cross-sectional view of a detail of half a smart cardaccording to one embodiment of the invention. Two recesses 12 a and 12 bof different depth for receiving a chip module are arranged in a cardbody 11. An antenna having an antenna connection 13 is laminated intothe card body 11, the antenna connection 13 being arranged below an edgeregion of the recess 12 a.

In a cutout 15 in the card body 11 that is arranged above the antennaconnection 13 in the manner of a slit or bore, there is arranged anadhesive part 14 made of elastic, conductive material, which ispreferably based on silicone or silicone-like material, having anoverall height 14 a, 14 b. The height fraction 14 b corresponds to theheight of the cutout 15, that is to say to the distance of the antennaconnection 13 from an upper edge region 15 a of the cutout 15. Theheight fraction 14 a corresponds to the distance of the upper edgeregion 15 a from the upper edge of the adhesive part 14 and ispreferably 0.05-0.15 mm.

FIG. 4 shows a cross-sectional view of the detail of the smart cardshown in FIG. 3, following installation of the smart card. Identicalcomponents or components having the same significance are designated bythe same references.

Once a chip module having module connections 17 and contact areas 18 onthe upper side in the edge region 16 a of the chip module 16 has beenpressed and thus adhesively bonded onto the card body 11, the adhesivepart 14 made of elastic, conductive material is pressed together in thedirection of the smart card thickness and pressed onto the twoconnections 13 and 17 under the application of pressure.

The volume size of the cutout 15 with its upper edge region 15 a and itslateral edge regions 15 b is dimensioned such that the adhesive part 14almost fills the entire cutout 15 when the module connection 17 isplaced on the upper edge region 15 a of the cutout 15, so that yieldingof the adhesive part 14 in the lateral direction—that is to say in thelongitudinal or width direction of the smart card—is not possible evenafter many years' use of the smart card. In this way, a permanentelectrical contact between the conductive, elastic adhesive part and themodule connections 13 and antenna connections 17 is maintained.

The smart card according to the invention that is shown here and theassociated production method furthermore have the advantage, compared tosmart cards and methods in which hot-melt adhesives are used, that inthe event of too many adhesive parts being applied, no lateral emergenceand contamination of the card surface is possible during implantation ofthe chip module, since the adhesive parts are already cured prior toinstallation of the chip module.

All the features disclosed in the application documents are claimed asbeing essential features of the invention in that they, individually orin combination, are novel with respect to the prior art.

1. A method of producing smart cards having a card body (11), at least one recess (12 a, 12 b) arranged therein for receiving at least one chip module (16) having module connections (17) in the edge region (16 a ) of the chip module (16) and a conductive structure body embedded in the card body (11) and having body contact connections (13), in particular an antenna having antenna connections which are arranged below the edge region (16 a ) of the chip module (16), characterized in that, prior to installation of the chip module (11), adhesive parts (14) made of elastic, conductive material are applied at points to the body contact connections (13) and/or the module connections (17) and cured, and then the chip module (11) is installed in the card body (11) with pressure being applied to the adhesive parts (14) made of elastic material.
 2. The method according to claim 1, characterized in that, prior to installation of the chip module (11), the adhesive parts (14) are applied so as to be about 0.05 to 0.15 mm higher than upper edge regions (15 a) of cutouts (15) arranged in the card body, which cutouts are designed to receive the adhesive parts (14).
 3. A smart card having a card body (11), at least one recess (12 a, 12 b) arranged therein for receiving at least one chip module (16) having module connections (17) in the edge region (16 a) of the chip module (16) and a conductive structure body embedded in the card body (11) and having body contact connections (13), in particular an antenna having antenna connections which are arranged below the edge region (16 a) of the chip module (16), wherein, with the chip module (16) installed between the module connections (17) on the one hand and the body contact connections (13) on the other hand, adhesive parts (14) made of conductive material are arranged between the connections (13, 17) characterized in that the adhesive parts (14) are made of elastic material, are applied at points, are cured prior to installing the chip module (16), with pressure being applied to produce a contact.
 4. The smart card according to claim 3, characterized in that the adhesive parts (14) are arranged within cutouts (15) which are arranged in the card body (11) below the edge region (16 a ) of the chip module (16) and at the bottom terminate with the body contact connections (13).
 5. The smart card according to claim 4, characterized in that the cutouts (15) have a volume size that is sufficient to completely receive the adhesive parts (14) under the application of pressure.
 6. The smart card according to claim 4, characterized in that in the direction of the card body thickness the cutouts (15) have height dimensions (14 b) that are smaller than the height (14, 14 b) of the adhesive parts (14) applied at points, without the application of pressure.
 7. The smart card according to claim 3, characterized in that the adhesive parts (14) form a resilient buffer in order to produce a permanent contact between the chip module connections (13) and body contact connections (17) following installation of the chip module (11).
 8. The smart card according to claim 3, characterized in that the adhesive parts (14) primarily act along the card body thickness as a resilient buffer. 